JP2006245001A - Electrolyte for lithium battery and lithium battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte for a lithium battery improved in safety of the battery, and also to provide the lithium battery containing the electrolyte. <P>SOLUTION: The electrolyte for the lithium battery contains a nonaqueous organic solvent, a lithium salt, a complex forming additive stable at 2.5-4.8 V and chelating with transition metals. The complex forming additive traps metal to prevent problems wherein the metal deposits on the surface of a negative electrode and generates drop in voltage and drop in safety by causing internal short circuit, and since safety in storage at high temperature is ensured, the electrolyte for the lithium battery and the lithium battery containing the electrolyte, safety of the battery such as overcharge characteristics is remarkably increased compared with existing nonaqueous electrolytes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrolyte for a lithium battery and a lithium battery including the same, and more particularly to an electrolyte for a lithium battery excellent in safety and a lithium battery including the same.

  Recently, with the reduction in size and weight of portable electronic devices, there is an increasing need for higher performance and larger capacity of batteries used as power sources for these devices. The lithium secondary batteries that are currently in commercial use are batteries with an average discharge potential of 3.7V, that is, 4V, and are rapidly applied to mobile phones called 3C, notebook computers, camcorders, etc. It is an element equivalent to the heart of the digital age.

  There is also active research to improve battery capacity and performance characteristics and improve safety such as overcharge characteristics. When a battery is overcharged, lithium is excessively deposited at the anode and lithium is excessively inserted at the cathode depending on the state of charge, and the anode and cathode become thermally unstable and the organic solvent of the electrolyte decomposes rapidly. Exothermic reactions and thermal explosions occur, causing serious problems in terms of battery safety.

  In order to solve such a problem, a method of adding an aromatic compound as a redox shuttle additive in an electrolyte is used. For example, Patent Document 1 discloses a non-aqueous lithium ion battery in which a benzene compound such as 2,4-difluoroanisole is added to prevent an overcharge current and a thermal explosion phenomenon caused thereby. In Patent Document 2, the stability of the battery is improved by adding a small amount of an aromatic compound such as biphenyl, 3-chlorothiophene, furan, etc. and electrochemically polymerizing in an abnormal overvoltage state to increase the internal resistance. A method for improving is disclosed. These redox shuttle additives have the effect of suppressing the overcharge reaction by quickly raising the internal temperature of the battery by heat generated from the oxidation exothermic reaction and shutting down the pores of the separator quickly and uniformly. To do. In addition, during overcharge, the polymerization reaction of the additive on the anode surface also functions to protect the battery by consuming overcharge current.

  However, as the capacity of batteries increases gradually in response to customer needs, it is becoming difficult for such overcharge additives to meet high levels of safety requirements (eg, overcharge additives). (Deterioration of high-temperature storage characteristics when adding phenyl acetate as an agent). Therefore, as the demand for higher capacity of batteries increases, there is an urgent need for a new overcharge additive capable of ensuring these safety and an electrolyte system including the same.

US Pat. No. 5,709,968 US Pat. No. 5,879,834

  Accordingly, the present invention has been made in view of such problems, and an object of the present invention is to provide an electrolyte for a lithium battery that can improve the safety of the battery.

  Another object of the present invention is to provide a lithium battery including the electrolyte.

  In order to solve the above problems, the present invention provides an electrolyte for a lithium battery comprising a non-aqueous organic solvent, a lithium salt, and a complex-forming additive that is stable at 2.5 to 4.8 V and chelates with a transition metal. .

  The lithium battery containing the electrolyte of the present invention is significantly superior in battery safety, such as overcharge characteristics, as compared to a battery using an existing non-aqueous electrolyte. The complex-forming additive collects the metal and prevents the metal from being deposited on the cathode surface, causing a voltage drop due to an internal short circuit and reducing safety, especially when left at high temperatures. Excellent effect in securing safety. In addition, 2.5-4.8V is the range of the general discharge / charging of a battery.

（前記化学式１〜前記化学式３中，Ｒ１，Ｒ２，Ｒ３，Ｒ４，Ｒ５およびＲ６は同一またはそれぞれ独立しており，Ｒ１〜Ｒ３の少なくとも一つおよびＲ４〜Ｒ６の少なくとも一つはＡＸＲ’（ＡはＮ，Ｏ，ＰまたはＳであり，ｘは０または１であり，Ｒ’はＣＮ，Ｃ１〜Ｃ１５の直鎖状または分枝状アルキル基またはカルボキシル基であり，残りはＨ，ハロゲン，Ｃ１〜Ｃ１５アルキルまたはＣ６〜Ｃ１５のアリール基である。）であり，
ｎは０〜１０の整数であり，
ｎ１は０〜１５の整数であり，ｎ１が奇数のときにａは１を示し，ｎ１が偶数のときにａは１／２または１を示す。） The complex-forming additive is preferably at least one of compounds represented by the following chemical formulas 1 to 3.

(In the chemical formula 1 to the chemical formula 3, R1, R2, R3, R4, R5 and R6 are the same or independent, and at least one of R1 to R3 and at least one of R4 to R6 are AXR ′ (A Is N, O, P or S, x is 0 or 1, R ′ is CN, a C1-C15 linear or branched alkyl group or carboxyl group, and the rest are H, halogen, C1 ~ C15 alkyl or C6-C15 aryl group).
n is an integer from 0 to 10,
n1 is an integer of 0 to 15, and when n1 is an odd number, a indicates 1, and when n1 is an even number, a indicates 1/2 or 1. )

（前記化学式４〜前記化学式２６中，Ｍｅはメチル基であり，Ｐｈはフェニル基である。） The complex-forming additive is preferably at least one of compounds represented by the following chemical formulas 4 to 26.

(In the chemical formulas 4 to 26, Me is a methyl group and Ph is a phenyl group.)

  The content of the complex-forming additive compound is preferably 0.1 to 10% by weight based on the total weight of the electrolyte.

  If the addition amount of the complex formation additive is less than 0.1% by weight, the effect of addition is insignificant. If the addition amount of the complex formation additive exceeds 10% by weight, there is a charge / discharge life problem. It is not preferable.

  The content of the complex-forming additive compound is more preferably 1 to 5% by weight with respect to the total weight of the electrolyte.

  The content of the complex-forming additive compound is more preferably 3 to 5% by weight with respect to the total weight of the electrolyte.

  The electrolyte preferably further includes an elution additive that elutes the transition metal from the anode.

  According to the present invention, the overcharge mode due to an internal short circuit can be completely switched to the shut-down mode to ensure overcharge stability.

  The elution additive is preferably an ester series compound.

  The elution additive is preferably selected from the group consisting of phenyl acetate, benzyl benzoate, ethyl acetate, 1-naphthyl acetate, 2-chromanone, and ethyl propionate.

  The amount of the eluting additive is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the whole electrolyte.

  If the addition amount of the elution additive is less than 1 weight, the effect of suppressing overcharge cannot be obtained, and if the addition amount of the elution additive exceeds 10 parts by weight, the life characteristics are deteriorated.

  The addition amount of the elution additive is more preferably 1 to 7 parts by weight with respect to 100 parts by weight of the whole electrolyte.

  The addition amount of the elution additive is more preferably 3 to 5 parts by weight with respect to 100 parts by weight of the whole electrolyte.

The lithium _{salt, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiClO 4, LiCF 3 SO 3, Li (CF 3 SO 2) 2 N, LiC 4 F 9 SO 3, LiAlO 4, LiAlCl 4, LiN ( C _x F _2x + 1SO ₂ ) (C _y F _2y + 1SO ₂ ) (where x and y are natural numbers), LiCl, and LiI are preferably one or more selected from the group consisting of LiI.

  Lithium salts act as a source of lithium ions in the battery to enable basic lithium battery operation, and non-aqueous organic solvents allow ions involved in the battery's electrochemical reactions to move. Serves as a medium.

  The lithium salt is preferably used at a concentration of 0.6 to 2.0M.

  If the concentration of the lithium salt is less than 0.6M, the electrolyte's degree of electrolysis decreases and the performance of the electrolyte deteriorates. If the concentration of the lithium salt exceeds 2.0M, the viscosity of the electrolyte increases and lithium ions increase. There is a problem that the mobility of the is reduced.

  The non-aqueous organic solvent is preferably at least one solvent selected from the group consisting of carbonates, esters, ethers and ketones.

  The carbonate may be at least one solvent selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propylene carbonate, ethyl propyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate. preferable.

  The non-aqueous organic solvent is preferably a mixed solvent of a carbonate solvent and an aromatic hydrocarbon organic solvent.

  The aromatic hydrocarbon organic solvent is preferably an aromatic compound represented by the following chemical formula 27.

  In the chemical formula 27, R10 is a halogen or an alkyl group having 1 to 10 carbon atoms, and q is an integer of 0 to 6.

  The aromatic hydrocarbon organic solvent is preferably at least one solvent selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, chlorotoluene and xylene.

The electrolyte further includes an additive selected from the group consisting of carbonate, vinylene carbonate, divinylsulfone and ethylene sulfite having a substituent selected from the group consisting of halogen, cyano group (Cn) and nitro group (NO ₂ ). Is preferred.

  When such a third additive is further included, a battery having excellent high-temperature swelling characteristics and electrochemical characteristics such as capacity, life, and low-temperature characteristics can be provided.

The electrolytic solution preferably further includes a carbonate additive having a substituent selected from the group consisting of halogen, cyano group (CN), and nitro group (NO ₂ ).

  The carbonate additive is preferably a carbonate of the following chemical formula 28.

In the chemical formula 28, X1 is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ).

  The carbonate additive is preferably fluoroethylene carbonate.

  The present invention also provides an anode including an anode active material capable of intercalating and deintercalating the electrolyte lithium, a material capable of intercalating and deintercalating lithium, lithium metal And a cathode comprising a cathode active material selected from the group consisting of a lithium-containing alloy and a material capable of reversibly reacting with lithium to form a lithium-containing compound.

  The lithium battery of the present invention is remarkably superior in battery safety, such as overcharge characteristics, as compared to a battery using an existing non-aqueous electrolyte.

  The cathode active material is preferably a carbon series material capable of inserting and extracting lithium ions.

  The lithium battery containing the electrolyte of the present invention is significantly superior in battery safety, such as overcharge characteristics, as compared to a battery using an existing non-aqueous electrolyte.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  This embodiment relates to an electrolyte for a non-aqueous lithium battery. The structure of a general non-aqueous lithium secondary battery 1 is as shown in FIG.

  The above battery is used as an anode 2 and a cathode 4 containing an active material capable of intercalating and deintercalating lithium. A separator 6 is inserted between the anode 2 and the cathode 4 and wound. After the electrode assembly 8 is formed, it is manufactured by placing it in the case 10. The upper part of the battery is sealed with a cap plate 12 and a gasket 14. The cap plate 12 may be provided with a safety valve (not shown) for preventing over-pressure formation of the battery, and a lead disposed between the cap plate 12 and the cap plate 12 via an insulating plate 26. The plate 24 is installed. The anode 2 of the electrode assembly 8 is electrically connected to a case 10 serving as an anode terminal by an anode tab 18, and the cathode 4 is electrically connected to a cathode terminal 22 by a cathode tab 20. Inject electrolyte before sealing the battery. The injected electrolyte is impregnated in the anode 2, the cathode 4 and the separator 6. As the separator, polyethylene, polypropylene, or a multilayer film of these polyethylene / polypropylene can be used.

  Lithium batteries may experience a thermal explosion phenomenon in which the temperature of the battery rapidly rises due to overcharging or short-circuiting due to a design defect of the battery itself due to misuse or failure of the charger. In particular, during overcharging, excessive amounts of lithium escape from the anode and deposit on the surface of the cathode, making both electrodes thermally unstable, resulting in thermal decomposition of the electrolyte, reaction between the electrolyte and lithium, The so-called thermal explosive phenomenon, in which an exothermic reaction takes place rapidly due to the electrolyte oxidation reaction at the anode and the reaction between oxygen and the electrolyte generated by the thermal decomposition of the anode active material, causing the battery temperature to rise, Exceeding the allowable temperature will lead to ignition and smoke of the battery.

  In order to solve these problems, various attempts have been made to add various additives such as overcharge additives and additives that improve high-temperature storage properties to the electrolyte. However, although the intended effect was obtained, there was a problem that an unforeseen defect occurred (for example, deterioration of the high temperature storage property when phenyl acetate as an overcharge additive was added). In addition, there has been a problem that a voltage drop occurs due to metal foreign matter that is not filtered in the battery manufacturing process.

  In the present embodiment, in order to solve such a problem, an additive capable of trapping metal or metal foreign matter eluted from the anode particularly during overcharge or when left at high temperature is electrolyzed. Used for liquid. The additive used for the lithium battery electrolyte of this embodiment is a complex-forming additive that is stable at 2.5 to 4.8 V and can form a complex by chelating with a metal. Such a complex-forming additive collects the metal and can prevent the problem that the metal is deposited on the cathode surface, causing a voltage drop due to an internal short circuit and lowering the safety. Excellent effect in ensuring safety when left unattended.

  As the complex forming additive, at least one of compounds represented by the following chemical formulas 1 to 3 is preferable.

  (In the above chemical formulas 1 to 3, R1, R2, R3, R4, R5 and R6 are the same or independent, and at least one of R1 to R3 and at least one of R4 to R6 are AXR ′ (A Is N, O, P or S, x is 0 or 1, R ′ is CN, a C1-C15 linear or branched alkyl group or carboxyl group, and the rest are H, halogen, C1 N is an integer from 0 to 10, n1 is an integer from 0 to 15, and when n1 is an odd number, a represents 1 and n1 A is 1 or 2 when is an even number.)

  As a more preferable complex-forming additive, at least one of compounds represented by the following chemical formulas 4 to 26 can be used.

  (In the above chemical formulas 4 to 26, Me is a methyl group and Ph is a phenyl group.)

  In the electrolyte of this embodiment, the content of the complex-forming additive compound is preferably 0.1 to 10% by weight, more preferably 1 to 5% by weight, most preferably 3 to 5% by weight based on the total weight of the electrolyte. preferable. If the addition amount of the complex formation additive is less than 0.1% by weight, the effect of addition is insignificant. If the addition amount of the complex formation additive exceeds 10% by weight, there is a charge / discharge life problem. It is not preferable.

  The lithium battery electrolyte of the present embodiment further includes an elution additive that elutes the transition metal from the anode as the second additive, that is, when both the complexing additive and the elution additive are used, an internal short-circuit occurs. It is preferable because the overcharge stability can be ensured by completely switching the overcharge mode to the shut-down mode.

  The elution additive is preferably an ester series compound, most preferably selected from the group consisting of phenyl acetate, benzyl benzoate, ethyl acetate, 1-naphthyl acetate, 2-chromanone and ethyl propionate.

  The addition amount of the elution additive is preferably 1 to 10 parts by weight, more preferably 1 to 7 parts by weight, and most preferably 3 to 5 parts by weight with respect to 100 parts by weight of the whole electrolyte. If the addition amount of the elution additive is less than 1 weight, the effect of suppressing overcharge cannot be obtained, and if the addition amount of the elution additive exceeds 10 parts by weight, the life characteristics are deteriorated.

  The electrolyte of this embodiment contains a lithium salt and a non-aqueous organic solvent. Lithium salts act as a source of lithium ions in the battery to enable basic lithium battery operation, and non-aqueous organic solvents allow ions involved in the battery's electrochemical reactions to move. Serves as a medium.

As the lithium _{salt, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiClO 4, LiCF 3 SO 3, Li (CF 3 SO 2) 2 N, LiC 4 F 9 SO 3, LiAlO 4, LiAlCl 4, LiN _{(C x F 2x + 1SO 2} ) (C y F 2y + 1SO 2) ( wherein, x and y are natural numbers), LiCl, and mixed to use one or more selected from the group consisting of LiI Is possible.

  The concentration of the lithium salt is preferably in the range of 0.6 to 2.0M, and more preferably in the range of 0.7 to 1.6M. If the concentration of the lithium salt is less than 0.6M, the electrolyte's degree of electrolysis decreases and the performance of the electrolyte deteriorates. If the concentration of the lithium salt exceeds 2.0M, the viscosity of the electrolyte increases and lithium ions increase. There is a problem that the mobility of the is reduced.

  As the non-aqueous organic solvent, carbonate, ester or ketone can be used. Examples of the carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propylene carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC ), Propylene carbonate (PC), butylene carbonate (BC) and the like, and as the ester, n-methyl acetate, n-ethyl acetate, n-propyl acetate and the like can be used.

  Among the non-aqueous organic solvents, in the case of a carbonate-based solvent, it is preferable to use a mixture of cyclic carbonate and chain carbonate. In this case, the cyclic carbonate and the chain carbonate are preferably mixed and used at a volume ratio of 1: 1 to 1: 9. When mixed in the above volume ratio, the performance of the electrolyte appears favorably.

  Moreover, the electrolyte of this embodiment can further contain an aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. As the aromatic hydrocarbon organic solvent, an aromatic hydrocarbon compound represented by the following chemical formula 27 can be used.

  (In the above chemical formula 27, R10 is a halogen or an alkyl group having 1 to 10 carbon atoms, and q is an integer of 0 to 6)

  As the aromatic hydrocarbon organic solvent, at least one solvent selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, chlorotoluene and xylene can be used.

The electrolyte of the present embodiment includes, as a third additive, carbonate, vinylene carbonate, divinyl sulfone, and ethylene sulfite having a substituent selected from the group consisting of halogen, cyano group (CN), and nitro group (NO ₂ ). An additive selected from the group consisting of: When such a third additive is further included, a battery having excellent high-temperature swelling characteristics and electrochemical characteristics such as capacity, life, and low-temperature characteristics can be provided. Among the above additives, a carbonate additive is preferable. As the carbonate additive, an ethylene carbonate derivative represented by the following chemical formula 28 is preferable, and fluoroethylene carbonate is most preferable.

(In the above chemical formula 28, X1 is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ).)

  The electrolyte of the present embodiment is produced by adding a lithium salt and the above additives to a non-aqueous organic solvent. The additive is generally added to the organic solvent in which the lithium salt is dissolved, but the order of addition of the lithium salt and the electrolyte additive is not important.

  The present embodiment provides a lithium battery including the electrolyte. As the anode active material of the lithium battery, a compound capable of reversible lithium intercalation / deintercalation (Li intercalation compound) can be used. As a cathode active material, it is possible to form a lithium-containing compound by reversibly reacting with a carbon series material capable of intercalating / intercalating lithium ions, lithium metal, a lithium-containing alloy or lithium. Can be used.

  The lithium battery of this embodiment can be a lithium primary battery or a lithium secondary battery.

  The lithium battery including the electrolyte according to the present embodiment has remarkably superior overcharge characteristics as compared with a battery using an existing non-aqueous electrolyte.

  Hereinafter, preferred examples and comparative examples of the present invention will be described. The following embodiment is only a preferred embodiment of the present invention, and does not limit the present invention.

(Comparative Example 1)
94 g of LiCoO 2 anode active material, 3 g of super-P conductive material and 3 g of polyvinylidene fluoride (PVDF) binder were dissolved in N-methyl-2-pyrrolidone to produce an anode active material slurry. The anode active material slurry was applied to an Al foil having a width of 4.9 cm and a thickness of 147 μm, dried and rolled, and then cut into predetermined dimensions to produce an anode.

  90 g of mesocarbon fiber (MCF: Petoca) cathode active material and 10 g of polyvinylidene fluoride binder were dissolved in N-methyl-2-pyrrolidone to produce a cathode active material slurry. The cathode active material slurry was applied onto a copper foil having a width of 5.1 cm and a thickness of 178 μm, and then dried and rolled, and cut into predetermined dimensions to produce a cathode.

A separator made of polyethylene film was placed between the manufactured anode and cathode, and this was wound to make an electrode assembly. After inserting this electrode assembly into the battery case, the liquid electrolyte was decompressed and injected to complete the battery. At this time, an electrolyte in which 1M LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and fluorobenzene (volume ratio of 3: 5: 1: 1) was used as the electrolyte. Further, 10 parts by weight of chlorotoluene was added to 100 parts by weight of the whole electrolyte, and 7 parts by weight of phenyl acetate was added.

  Three batteries according to the above Comparative Example 1 were manufactured. 1-No. 3 was measured, and the OCV, IR and battery thickness after standard charging and the OCV, IR and battery thickness after standing at 85 ° C. for 4 hours were measured. The results are shown in Table 1.

  As shown in Table 1, in the case of Comparative Example 1 using only phenyl acetate, the OCV significantly decreased when left at high temperature, and the thickness of the battery greatly increased. That is, it can be seen that the swelling phenomenon is intense.

(Comparative Example 2)
A lithium secondary battery was completed in the same manner as in Comparative Example 1 except that phenyl acetate was not used.

(Experimental example 1)
The cyclic voltammetry of succinonitrile was measured three times at a rate of 0.5 mV / sec using glassy carbon as the working electrode and metallic lithium as the reference electrode and the counter electrode. It was shown in 2. As can be seen from FIG. 2, succinonitrile does not show a specific redox peak between 2.5 and 4.8 V, indicating that it is a stable compound within this range.

(Experimental example 2)
The anode manufactured in the above Comparative Example 1 was charged as a standard, then immersed in an electrolytic solution, added together with phenyl acetate and the complexing additive shown in Table 3 below, and allowed to stand at 85 ° C. for 4 hours to prepare an electrolytic solution. The results of observation of the colors are shown in Table 2.

  From the results shown in Table 2, it is judged that after cobalt is eluted, a complex is formed and a hue change occurs. In Table 2 above, it is presumed that the amine system reacts with the electrolytic solution and turns dark brown.

Example 1
An electrolyte prepared by adding succinonitrile to a 1M LiPF ₆ dissolved ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate: fluorobenzene mixed solvent (3: 5: 5: 1 volume ratio) was used. A lithium secondary battery was completed by the same method as in Comparative Example 1 except for the above. At this time, the addition amount of the succinonitrile additive was 5% by weight with respect to the weight of the whole electrolyte.

(Example 2)
It was prepared by further adding succinonitrile and phenyl acetate to a mixed solvent of ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate: fluorobenzene (3: 5: 5: 1 volume ratio) in which 1M LiPF ₆ was dissolved. A lithium secondary battery was completed in the same manner as in Example 1 except that the electrolyte was used. At this time, the addition amount of the succinonitrile additive was 5% by weight with respect to the weight of the whole electrolyte, and the addition amount of the phenyl acetate was 3 parts by weight with respect to 100 parts by weight of the whole electrolyte.

(Example 3)
The same procedure as in Example 1 was carried out except that 3-ethoxy-propionitrile (EPN) was used instead of succinonitrile in an amount of 5% by weight based on the weight of the total electrolyte.

Example 4
The same procedure as in Example 1 was performed except that ethylene glycol diacrylate (EGDA) was used in an amount of 5% by weight based on the total electrolyte weight instead of succinonitrile.

(Example 5)
Implementation was performed except that 1,2-bis (diphenylphosphono) ethane (DPPE, 1,2-Bis (diphenylphosphino) ethane) was used instead of succinonitrile in an amount of 5% by weight based on the weight of the total electrolyte. Performed as in Example 1.

(Example 6)
The same procedure as in Example 1 was conducted except that 1,2-dibromoethane (DBE, 1,2-Dibromoethane) was used in an amount of 5% by weight based on the weight of the entire electrolyte instead of succinonitrile.

  After overcharging the lithium batteries of Example 2 and Comparative Example 1 at 1.5 C, the voltage and temperature according to the operating time were measured, and the results are shown in FIG. From FIG. 3, it can be seen that the lithium battery of Comparative Example 1 to which only phenyl acetate was added had a very unstable voltage and a very high battery temperature depending on the operation time, and therefore the battery safety was not good. In contrast, the battery of Example 2 using both phenyl acetate and succinonitrile is found to be excellent in battery safety because the operating voltage is uniform and the battery temperature is much lower than that of Comparative Example 1.

  Moreover, the high temperature leaving experiment which leaves the battery of Examples 1-6 and Comparative Examples 1-2 at 85 degreeC for 4 hours was conducted. In addition, overcharge experiments were performed on the batteries manufactured in the above Examples and Comparative Examples. In the overcharge experiment, after the manufactured battery was fully charged to 4.2 V, a Ni tab was resistance welded to each terminal to form a lead wire, and connected to a charger / discharger. The battery was overcharged to 5 C (1.6 A) / 12 V, and after reaching 12 V, the current was continuously applied for 2.5 hours to observe the ignition and explosion of the battery. The results are shown in Table 3. In Table 3, the criteria for overcharge safety evaluation are as follows. In Table 3, the unit of standard capacity is mAh.

  L0: Good, L1: Leakage, L2: Flash, L2: Spark, L3: Smoke, L4: Ignition, L5: Rupture

  As shown in Table 3, it can be seen that Example 2 using both succinonitrile and phenyl acetate is most excellent in high temperature storage and overcharge safety. In Examples 3 to 6 in which phenyl acetate was not added, all of the high temperature storage characteristics were satisfied, and the overcharge safety was not satisfied up to L0, but Comparative Example 2 in which no additive was used. It can be seen that there is a slight improvement compared to.

  In the case of Comparative Example 2 in which no additive was used, the high temperature storage characteristics were satisfied, but the overcharge safety was not very good. In the case of Comparative Example 1 using only phenyl acetate, It can be seen that the overcharge safety is excellent, but the high-temperature storage characteristics are not good.

  The OCV, IR and thickness after standard charging were measured for the batteries of Example 2 and Comparative Example 2 above, and the OCV, IR and thickness (85 ° C. and room temperature) after being left at 85 ° C. for 4 hours were measured. The results are shown in Table 4. In addition, the capacity after standard charge / discharge (STD DC), the discharge capacity ret (DC) measured immediately after standing at high temperature and after cooling to room temperature, and the capacity measured by discharging, charging and discharging after standing at high temperature. The results of rec (DC) are also shown in Table 4. In Table 4, ret (DC) is an experiment for confirming how much the charging capacity is maintained, and rec (DC) is for confirming how much the capacity is maintained after being left at a high temperature. This is an experiment. In Table 4, the unit of OCV is V, the unit of IR is mohm, and the unit of STD DC, ret (DC), and rec (DC) is mAh.

  As shown in Table 4, it can be seen that the battery of Example 2 exhibits substantially the same level of battery physical properties as the battery of Comparative Example 2. Therefore, it can be seen from the results of Tables 3 and 4 that when both succinonitrile and phenyl acetate are used, it is possible to ensure high temperature storage and overcharge safety while maintaining the battery physical properties.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Acknowledge.

  The present invention can be applied to an electrolyte for a lithium battery and a lithium battery including the electrolyte. More specifically, the present invention can be applied to an electrolyte for lithium battery excellent in safety and a lithium battery including the electrolyte.

It is the schematic of the structure of a common non-aqueous lithium battery. It is explanatory drawing which shows the cyclic voltammetry measurement result of a succinonitrile in Experimental example 1 of one Embodiment of this invention. It is explanatory drawing which shows the electric current, temperature, and voltage characteristic at the time of carrying out 1.5C overcharge of the lithium battery which concerns on Example 2 and comparative example 2 of one Embodiment of this invention with a graph.

Explanation of symbols

1 Nonaqueous Lithium Secondary Battery 2 Anode 4 Cathode 6 Separator 8 Electrode Assembly 10 Case 12 Cap Plate 14 Gasket 16 Safety Valve 18 Anode Tab 20 Cathode Tab 22, 24 Insulator 26 Electrolyte 22 Cathode Terminal 24 Lead Plate 26 Insulating Plate

Claims (44)

A non-aqueous organic solvent,
Lithium salt,
An electrolyte for a lithium battery, characterized by comprising a complex-forming additive that is stable at 2.5 to 4.8 V and chelates with a transition metal. 2. The electrolyte for a lithium battery according to claim 1, wherein the complex-forming additive is at least one of compounds represented by the following chemical formulas 1 to 3.

(In the chemical formula 1 to the chemical formula 3, R1, R2, R3, R4, R5 and R6 are the same or independent, and at least one of R1 to R3 and at least one of R4 to R6 are AXR ′ (A Is N, O, P or S, x is 0 or 1, R ′ is CN, a C1-C15 linear or branched alkyl group or carboxyl group, and the rest are H, halogen, C1 ~ C15 alkyl or C6-C15 aryl group).
n is an integer from 0 to 10,
n1 is an integer of 0 to 15, and when n1 is an odd number, a indicates 1, and when n1 is an even number, a indicates 1/2 or 1. ) The lithium battery electrolyte according to claim 2, wherein the complex-forming additive is at least one of compounds represented by the following chemical formulas 4 to 26.

(In the chemical formulas 4 to 26, Me is a methyl group and Ph is a phenyl group.)   2. The electrolyte for a lithium battery according to claim 1, wherein a content of the complex-forming additive compound is 0.1 to 10 wt% with respect to a total weight of the electrolyte.   5. The electrolyte for a lithium battery according to claim 4, wherein a content of the complex-forming additive compound is 1 to 5 wt% with respect to a total weight of the electrolyte.   6. The electrolyte for a lithium battery according to claim 5, wherein a content of the complex-forming additive compound is 3 to 5 wt% with respect to a total weight of the electrolyte.   The electrolyte for a lithium battery according to claim 1, wherein the electrolyte further includes an elution additive for eluting the transition metal from the anode.   8. The electrolyte for a lithium battery according to claim 7, wherein the elution additive is an ester series compound.   9. The elution additive according to claim 8, wherein the elution additive is selected from the group consisting of phenyl acetate, benzyl benzoate, ethyl acetate, 1-naphthyl acetate, 2-chromanone, and ethyl propionate. Lithium battery electrolyte.   The electrolyte for a lithium battery according to claim 7, wherein the amount of the eluting additive is 1 to 10 parts by weight with respect to 100 parts by weight of the whole electrolyte.   11. The electrolyte for a lithium battery according to claim 10, wherein the addition amount of the elution additive is 1 to 7 parts by weight with respect to 100 parts by weight of the whole electrolyte.   The electrolyte for a lithium battery according to claim 11, wherein the amount of the eluting additive is 3 to 5 parts by weight with respect to 100 parts by weight of the whole electrolyte. The lithium _{salt, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiClO 4, LiCF 3 SO 3, Li (CF 3 SO 2) 2 N, LiC 4 F 9 SO 3, LiAlO 4, LiAlCl 4, LiN ( C _x F _2x + 1SO ₂ ) (C _y F _2y + 1SO ₂ ) (where x and y are natural numbers), LiCl, and LiI, and one or more selected from the group consisting of LiI The electrolyte for a lithium battery according to claim 1.   The electrolyte for a lithium battery according to claim 1, wherein the lithium salt is used at a concentration of 0.6 to 2.0M.   2. The electrolyte for a lithium battery according to claim 1, wherein the non-aqueous organic solvent is at least one solvent selected from the group consisting of carbonates, esters, ethers, and ketones.   The carbonate is at least one solvent selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate. The lithium battery electrolyte according to claim 15, wherein the electrolyte is a lithium battery electrolyte.   2. The electrolyte for a lithium battery according to claim 1, wherein the non-aqueous organic solvent is a mixed solvent of a carbonate-based solvent and an aromatic hydrocarbon-based organic solvent. The electrolyte for a lithium battery according to claim 17, wherein the aromatic hydrocarbon-based organic solvent is an aromatic compound represented by the following chemical formula 27.

(In said chemical formula 27, R10 is a halogen or a C1-C10 alkyl group, and q is an integer of 0-6.)   The aromatic hydrocarbon-based organic solvent is at least one solvent selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, chlorotoluene and xylene. The electrolyte for lithium batteries as described. The electrolyte further includes an additive selected from the group consisting of carbonate, vinylene carbonate, divinylsulfone and ethylene sulfite having a substituent selected from the group consisting of halogen, cyano group (Cn) and nitro group (NO ₂ ). The electrolyte for a lithium battery according to claim 1, characterized in that: 21. The lithium battery according to claim 20, wherein the electrolyte further includes a carbonate additive having a substituent selected from the group consisting of halogen, cyano group (CN), and nitro group (NO ₂ ). Electrolytes. 21. The electrolyte for a lithium battery according to claim 20, wherein the carbonate additive is a carbonate of the following chemical formula 28.

(In the chemical formula 28, X1 is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ).)   The lithium battery electrolyte according to claim 22, wherein the carbonate additive is fluoroethylene carbonate. An electrolyte comprising a non-aqueous organic solvent, a lithium salt, and a complexing additive that is stable at 2.5-4.8 V and chelates with a transition metal;
An anode containing an anode active material capable of intercalating and deintercalating lithium;
Selected from the group consisting of materials capable of intercalating and deintercalating lithium, lithium metal, lithium-containing alloys, and materials capable of reversibly reacting with lithium to form lithium-containing compounds. A lithium battery comprising a cathode containing a cathode active material. The lithium battery according to claim 24, wherein the complex-forming additive is at least one of compounds represented by the following chemical formulas 1 to 3.

(In the chemical formula 1 to the chemical formula 3, R1, R2, R3, R4, R5 and R6 are the same or independent, and at least one of R1 to R3 and at least one of R4 to R6 are AXR ′ (A Is N, O, P or S, x is 0 or 1, R ′ is CN, a C1-C15 linear or branched alkyl group or carboxyl group, and the rest are H, halogen, C1 ~ C15 alkyl or C6-C15 aryl group).
n is an integer from 0 to 10,
n1 is an integer of 0 to 15, and when n1 is an odd number, a indicates 1, and when n1 is an even number, a indicates 1/2 or 1. ) The lithium battery according to claim 25, wherein the complex-forming additive is at least one of compounds represented by the following chemical formulas 4 to 26.

(In the chemical formulas 4 to 26, Me is a methyl group and Ph is a phenyl group.)   [25] The lithium battery according to claim 24, wherein a content of the complex-forming additive compound is 0.1 to 10% by weight with respect to a total weight of the electrolyte.   The lithium battery according to claim 27, wherein the content of the complex-forming additive compound is 1 to 5% by weight based on the total weight of the electrolyte.   The lithium battery according to claim 28, wherein the content of the complex-forming additive compound is 3 to 5% by weight based on the total weight of the electrolyte.   25. The lithium battery of claim 24, wherein the electrolyte further includes an elution additive that elutes the transition metal from the anode.   The lithium battery according to claim 30, wherein the eluting additive is an ester series compound.   32. The elution additive of claim 31, wherein the elution additive is selected from the group consisting of phenyl acetate, benzyl benzoate, ethyl acetate, 1-naphthyl acetate, 2-chromanone, and ethyl propionate. Lithium battery.   The lithium battery according to claim 30, wherein the amount of the eluting additive is 1 to 10 parts by weight with respect to 100 parts by weight of the entire electrolyte.   The lithium battery according to claim 33, wherein the amount of the eluting additive is 1 to 7 parts by weight with respect to 100 parts by weight of the entire electrolyte.   The lithium battery according to claim 34, wherein the amount of the eluting additive is 3 to 5 parts by weight with respect to 100 parts by weight of the entire electrolyte.   The lithium battery according to claim 24, wherein the non-aqueous organic solvent is at least one solvent selected from the group consisting of carbonates, esters, ethers, and ketones.   The carbonate is at least one solvent selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate. The lithium battery according to claim 36, characterized in that   The lithium battery according to claim 24, wherein the non-aqueous organic solvent is a mixed solvent of a carbonate-based solvent and an aromatic hydrocarbon-based organic solvent. The lithium battery according to claim 38, wherein the aromatic hydrocarbon-based organic solvent is an aromatic compound represented by the following chemical formula 27.

(In said chemical formula 27, R10 is a halogen or a C1-C10 alkyl group, and q is an integer of 0-6.)   The aromatic hydrocarbon-based organic solvent is at least one solvent selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, chlorotoluene, and xylene, according to claim 39, The lithium battery as described. The electrolyte further includes an additive selected from the group consisting of carbonate, vinylene carbonate, divinylsulfone and ethylene sulfite having a substituent selected from the group consisting of halogen, cyano group (Cn) and nitro group (NO ₂ ). The lithium battery according to claim 24, characterized in that: The electrolyte, halogen, characterized in that it further comprises a carbonate additive having a substituent gas which is selected from the group consisting of cyano group (CN) and a nitro group (NO _2), a lithium battery of claim 41. 43. The lithium battery of claim 42, wherein the carbonate additive is a carbonate of formula 28 below.

(In the chemical formula 28, X1 is selected from the group consisting of halogen, cyano group (CN) and nitro group (NO ₂ ).)   The lithium battery according to claim 24, wherein the cathode active material is a carbon series material capable of inserting and extracting lithium ions.

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